Deuterium excess in subtropical free troposphere water vapor: Continuous measurements from the Chajnantor Plateau, northern Chile. Issue 23 (10th December 2014)

• Record Type: Journal Article
• Authors: Samuels‐Crow, Kimberly E.; Galewsky, Joseph; Sharp, Zachary D.; Dennis, Kate J.
• Is Part Of: Geophysical research letters. Volume 41:Issue 23(2014:Dec.)
• Page Start: 8652
• Page End: 8659
• Publication Date: 2014-12-10
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2014GL062302
• Languages: English
• ISSNs: 0094-8276

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Water vapor measured continuously by cavity ring‐down spectroscopy from July 2012 to March 2013 on the hyperarid Chajnantor Plateau, northern Chile (elevation = 5080 m, pressure ≈ 550 hPa), has a mean deuterium excess (<italic>d</italic>‐excess = <italic>δD</italic> − 8*<italic>δ</italic>¹⁸O) of 46‰ ± 5‰ and frequently exceeds 100‰ at low water vapor mixing ratios (<italic>q</italic> ≤ 500 ppmv). These measurements provide empirical support for theoretical predictions of free troposphere <italic>d</italic>‐excess. The <italic>d</italic>‐excess measured at this site can be understood in terms of supersaturation with respect to ice at relative humidities between 100% and 130%, followed by mixing with moist midtropospheric or lower tropospheric air en route to the plateau. The <italic>d</italic>‐excess measured at Chajnantor is consistent with predictions for <italic>d</italic>‐excess in the upper troposphere from isotope‐enabled general circulation models and with high vapor saturation over ice in cloud‐resolving and microphysical models.</p> </abstract>